Subscriber-response unit

ABSTRACT

A subscriber response unit (SRU) is disclosed wherein data may be communicated to and from a central control system or message center. The SRU responds only the received data properly address coded for that particular unit. Information entered into the SRU locally is automatically read out to the message center in response to an interrogation signal from the message center. The SRU is able to accept both high and low data input rates and can store information for future use. Further, the SRU can perform switching or controlling operations in response to properly address coded signals from the message center.

:ited States Patent 13,623,003

inventor T LHewln 3.$4l.5l3 I! m... BQOIITZJX ScfiaedndxNX. 3.539.9981mm kkllel'etd. 340M715 W Primary Exam-M D. SEW

filed Mn. 3, I970 Animal E Pamazed Nov. 23. I97] Allomeys-joha F.Aha-ELM A. FrankJuiusl.

laskalicky.fmkl.m,0scarlwaddelanll Joseph B. For-a SUBSCRIBER-RESPONSEUNIT M 6 ABSTRAC'IE A manu unit (saw) a; ma U51 340/1725 wherein datamay be mmmanicated to and from a centml Int. H043 3/00 control system orsang: center. The SRU respon ds only amuse-m; 340/1725. receiwd dam PM Mended for M p 15!, [63 Information Miami-25R! iucafly is Morgana" readout to the message center in response to an Interrogation datum cuedsignal from the meszg: center. The SRU '5 able to accept UNITED STATESPATENTS both high and low data i=pu! rates and can store infizgnzmonmtfiaJheSRUcanperiornswi: ingot .11 12/1910 mum et al 340/!51 "9" M F.535 4/1970 Holden el al. 340/163 W n W TWP W signals from the mm.

MESSAGE CENTER suescmazh um DISPLAY m MESSAGE GENERATOR gfggg w f PULSEWIDTH coon.

l 1 22 3! H INFORMATION 1 L ASS Puma-um: Low-Pass 7 PROCESSOR FILTERcEcwfii nus! 2/ I4 I I RECEIVER RmsunTEnqg m mam-ER rv msmxaunou wSYSTEM PAIENTEBuuv 23 I91! SHEETZBFS N GE ms AT'IDRNEYSUBSCRIBER-RESPONSE UNIT 11:: Invention relates to a subscriber responseunit for use a digital information distribution system. Such a unit actsas an innrfaoe between a human user and a central information station. Asystem utilizing the subscriber response unit (SRU) i intended tocomplement audio/visual communication techniques, such as television. toprovide the user with as complete an information interchange system aspossible, this in to being used as an information interchange system isitsown right.

In considering such a system, one must provide a subscriber responseunit that is compatible with existing communication equipment andflexible in operation. Further, the SRU must be capableof accepting catafrom a variety of sources; for example, the high speed data rate of themessage center and the rehtively low speed data rate from a humanoperator. The multiple rate acceptability of an SRU is necessary toenable a large number of SRUs to be utilized with a single messagecenter. The flexibility of operation is desirable so that the SRU may beapplied to a wide variety of uses. For example, it is desirable to havean SRU that displays the information received or transmitted so that theuser may readily use such infonnation. Further, the unit should becompatible with a variety of input/output devices used to provide ahuman interface to the SRU and to perfonn a variety of operationsautomatically. Further, it is desirable to provide an SRU with thecircuitry to carry out its functions with a minimum of error.

In view of the foregoing, it is therefore an object of the presentinvention to provide an SRU of maximum flexibility of operation.

it is a further object of the present invention to provide an SRUcompatible with a wide variety of input/output devices.

It is another object of the present invention to provide an SRUcompatible with existing communication technology.

it is a further object of the present invention to provide an SRU thatis address-coded and capable of receiving very high data input rates soas to minimize the time of the message center that isoccupicd by a givenSRU.

The foregoing objects are achieved in the present invention whereinthere is provided an SRU comprising address recognition means, functionselection means, data storage means, local data input means, displaymeans, and clock converter means all interrelated so that thev SRU can,upon being properly addressed by a signal from the message center,determine the funct'mn to be performed and carry it out. For example, iflocal information has been inserted by the local data input means andstored in the data storage register, the message center can address theparticular SRU and request it to read out any local information it maycontain. The particular SRU then performs this function and, uponindication of a correct transmission by the message center, receives a"clear" signal from the message center enabling the SRU to clear itsdata storage member of the transmitted information.

in addition to such infonnation exchange functions, as exemplilied bythe above, the SRU can also perform a variety of control functions. Forexample, the particular SRU, suitably addresed, may be told to perform aparticular switching function at its remote location. A suitable signalis then sent back to the message center indicating the performance ofthe assigned task. As is apparent from the above brief examples, theflexibility of the SRU is limited only by the input/output device usedat its location.

A more complete understanding of the present invention may be obtainedby considering the following detailed description taken in conjunctionwith the attached drawings in which:

FIG. 1 illustrates a wideband nformation distribution system.

Fit). 2 is a simplified block diagram of an SRU showing keyboard dataentry and "read" operation.

H6. 3 is a functional block diagram of an SRU illustrating data entry.

FIG. 4 is a functional block diagram of an SRU illustrating tlze readoperation.

FIGSisafimctionolHocifispaosofanSRUillcnsting theclear" operation.

m.6isafunctiosnlliockrapa-ofanSRUillustrating the command functirn.

'Ihesubscriberrespomeua'liatermmaldevicemed to communicate dais so andfrom acentral control system. or message center, via a CATV conrialcableor comparable broadband communication iii. In a typical communicationsystem, one message center may act a the control center for thousands ofSRU; A8 of the SRU; are interrogated once each scanning cycle by themesage center and the interrogations may take place over one or more ofthe channels available within the broadband link. Obviously. if desired,provision could be made for the interrogations to take place more orless frequently, depending upon subscriber usage. Thus, for example, aninactive SRU may be interrogated every second or third scanning cycle.This increases service to subscribers making use of their SRU andincreases the number of SRU's list may be serviced by a message (2112:.

Each SRU responds only to an input signal which contains its own uniqueaddrea In the simplest form of system scanning, the addres is differentfor each mesage transmitted, so that for cad: scanning cycle each of theSRU's in the system has been interrogated at least once. The inputsignal also contains information to command certain functions to beperformed. Asarmltoftltsse commands the SRU may transmit data back tothe mesage center, it may cause incoming data to be displayed in someform at the subscriber's site, or it may initiate the performance ofcertain switching or controlling operations.

One type of system iiltntrating the cable communication concept is shownin H0. I. The message generator ll at the message center generates thedigital information to be transmined to the SRU's through the coaxialnetwork. This information consists of the clock, the address of the SRU,the function to be performed by the SRU. and any infonnation which maybe waiting for transm fion to that particular SRU. In addition, a"reset" signal can be sent at the beginning of each message in order toseparate messages and provide a means of synchronizing system operationThe message format contains three parts: RESET, CLOCK, and DATA. Theseparts are combined into a pulse-width coded digital signal in coder II.The coded signal is next liltered by a low-pass filter 13 to reduce thebandwidth requirements and thus increase the number of possible signalchannels in the available frequency spectrum. With a pulse-widthmodulation format, the minimum bandwidth of the filter is twice that ofthe clock frequency in orrkr to preserve the time relationship of theunfiltered signal.

A carrier signal is modulated by the output of the low-pass filter intransmitter 14 and the resulting amplitude-moduli ted signai is sent outover the cable distribution system l5. This signal may be combined withany othersignals, including TV, to be transmitted in the forwarddirection. The current frequency band for transmission in the forwarddirection is about 30-250 mHz.

Upon arrival at the subscriber terminal, the signal is first separatedby a receiver 1 andarnplilied. The resulting signal is then pulse widthdecoded it decoder 7 to produce the three separate signals which aresent to the SRU 20. These three signals are RESET, CLOCK, and DATA. TheDATA signal contains the addres, function, and any incoming informationbeing sent to that termini.

The SRU 20 then res ends to the incoming signal. A common action is tosend data back to the message center The outgoing signal generated bythe SRU can be left as a non return-to-zero signal who: only function isto carry a return DATA signal. Since the system is synchronized there isno need toretum the CLOCK and RESET components. The not return-to-zeroDATA signal is filtered by filter l8 and used to moduhte a carrier forby transmitter i9 in the reverse direction back to the message center.The reverse uamissionbandcoventhefiequeneyrange ofabout 5-30 Ill-la.Atthemasageeenterthetigml is received in receiver 21 and procesed byproeemorn At the subscriber locat'aat. suitable display devices 23 servelidisplay theinforrnationbcallyentered into theSRU 20 by data inputdevices 24 and the information received from themesaageeentenAswibemorefullydescribed below.thedisplay devicu 23 can beused to display the locally generatedsignaluntil'lhasheencu'rectlyreeeivedbythemesage center, uponinterruption therefrom. This serves to indicate b the operator that themessage has been correctly received.

lnsummarinngtheopetatbnofthe SRU. it should be noted that the SRU ha twobas'c modes of operation, dependinguponthemanneriawhiehdataentersandleavesThedata may either be enteredlocally at the SRU (through a keyboard. for example) or may enter viathe incoming signal from the message center. When data is enteredlocally, it is normally entered slowly and randomly. one alpha-numericcharacter at a time. When the SRU k interrogated this information isread out and sent to the mesage center at a high data rate. Conversely.ifthe data is entered vn the incoming signal it enters at a high datarate and is then used at the SRU in a variety of possible ways usuallyat a relatively slow output data rate.

The wideband information distribution system, envisioned for use withthe SRU. is a synchronized system so that proper operation and evenkeyboard data entry depends upon the presence of the signal from themesage center, whether or not that particular SRU is being interrogatedma] entry of data,

via a keyboard. for example, is synchronized by the incoming Inesage butdoes not require that the message be addressed for that SRU. However,data entry into the SRU from the mesage center can occur. only if theSRU is conectly addressed A number of operations within the SRU dependupon either. or both. of two features of the incoming signal, The firstof these is the RESET pulse which occurs at the beginning of each mesageinterval. The second feature is that the first bit ofeach mesageisalwaysakigicfl."

The CLOCK signal provides the clock used for moving data through theSRU. There is no cloclt signal generated internally in the SRL'. Thus.clock generator ap aratus is eliminated as well as the synchronizingapparatus needed to synchronize a local cloclr with the incoming mesage.

The DATA signal coincides in time with the CLOCK signal. The first mbits of the DATA signal contain the FUNCTION information with the firstbitalways a logic l as mentioned previously. The next it hits containthe ADDRESS information. If data is to be entered into the SRU from themessage center this data follow the ADDRESS, otherwise any bit sequencefollowing the ADDRESS is disregarded by the SRU. In either case. theCLOCK must persist for a sufficient time after the end of the ADDRESS inorder that data may be moved out of the SRU and sent to the messagecenter.

As data is entered locally it is stored in the SRU until a TRANSMTTsignal is given by the operator. The SRU then waits tor the next mesagewhich contains a READ function and the same ADDRESS as that wired intothe unit. The SRU will then respond by returning the incoming FUNCTIONand ADDRESS code followed by bits representing the information locallyentered into the SRU. As the stored information is transmitted out ofthe SRU it is also recirculated back intonorageintheeventitrnustbermdagain.

Atthemessagecentertheretumsignalisprocessedandif the signal containsinformation in addition to the FUNCTION and ADDRESS bits wh'arh weresent. the message center will retransmit to the same SRU but this timewith a CLEAR function code which will then automatically reset the SRUand clear the readout. This indie-am to the user of the SRU thatthemessagehrnbeenreeeivedatthemessage center.

At any time before the mesage is transmitted from the SRU informationwhich has been entered via the keyboard may be cleared byenteringaCLEARsgnal into the SRU.

To transmit infontmionfiornthemesagecenwfa' storage in theSRUtheMANDItmctioneodeissera along with the ADDRBS not. When thiscombination occurmthenext followingbiseunain'ngthe'mformationareen- 5tered into storage in the SRU.

MostofthetystemoperatimsdtheSRUanbedacribedthroughanexplanationofthebcfldataerttryandREAD operation. A simplifiedblock diqrant dthis portion d the SRUisshowninFlGJ.

' The three componenuoftheiarutlrontthe rncsageeenter As pointed out inconnection will no.1. the pulse width decoder processes the signal atthe strlncribers location and produces three separate signal: RBET.DATA. and CLOCK. These three signals are coupled. respectively. to threeof the inputs 25, 26. and 17 to the SRU. The beginning of each messageinterval is marked by the RESET pulse. At this time a number offlip-flops are reset. including the READ flip-flop 28 shown in FIG. 2.The ADDRESS md FUNCTTON shifl registers 29 and 30. respectively, arealso cleared of any previ- 5 ous data which they may still hold. TheCLOCK and DATA signals follow the end of the RESET pulse. The CLOCKsignal is first converted as may be necessary for driving the shiftregisters used in the SRU. An A clock oonvener 3| is used for providingthis clock.

30 The clock pulses move the DATA signal through the AD- DRESS shiftregister 29 and the HJNCTTON shift register 30. After a given number ofclock pulses, detennined by the capacities of the registers 29 and 30.the registers are fully loaded with the DATA signal from input 26. Theoutputs of the shift registers 29 and 30 go to respective inputs of AD-DRESS and FUNCTION gates 31 and 32. respectively. The particularfunction gate shown "n FIG. 2 is the READ gate. There are two otherfunction gates in the SRU. one for CLEAR and one for COMMAND.

If the incoming data signal contains the proper ADDRESS sequence forthat particular SRU. the output of ADDRESS gate 3! will go to a logic"I." lfthe incoming data sequence contains the proper sequence for theREAD function. the output ofREAD gate 32 willgotoalogicl."Also.asthelast bit 5 of data is shifted into the registers.the last (right-hand most) stage of the FUNCTION shift reg'ster will bea I because, as mentioned above, Lthe first DATA bit is always a logic"I." The outputs of the ADDRESS and FUNCITON o gates and the outputofthe last stage ofthe FUNCTION shift register are applied as inputs toAND gate 33. which acts as a read control gate. Since all the inputs area logic "I," the output of AND gate 33 goes to a bgic l, therebyactivating READ flip-flop 28.

The output of the READ flip-flop performs three functions. First, whenthe READ flip-flop go: into the logic l'state, it opens gate 34 andallows the info mation to flow out of shift register 30. through gate34. and out to the return transmitter for transmission to themessagecenkr. At the same time. the

output of the READ flip'llop causes switch 35 to change to the upperterminals. thus disconnecting the input ofthe AD- DRESS shift register29 from the iteoming DATA signal and connecting it to the output of thedatastotage shifi register 36- The READ flip-flop 28isahoconnectedtothereadoutsec- 5 tion ofB" clock converter 37v l'the TRANSMTI' signal hasbeen locally entered, the clock manner will be turned on and the localclock output wit transfer data out of the data storage shift registerand into the ADDRESS shift register 29 from where it proceeds throughthe FUNCTION shift registergate34.andontothetransmitterfortransmissiontothe message center. As thedata is being transferred out of the data storage shift register 36. 'lis 850 be'mg recirculated back into the input of the shift register viainput 360 so that after transmission the data will so] be it II: datastorage shitt register 36 in the event it must hereadagairL'The "B'clockccnverter 37 will continue to produce clock pulses until i i turned off.This turnoff is accomplished by a pulse from the termediate register andcounter 38 which counts the number of clock pulses necessary to read outthe data from data storage register 36, and then produces an outputpulse. It is, course, necessary that throughout this time the input Clmsignal continues so that the local clock pulses may be generated. Thus.the output signal returned by the SRU to the mmage center in response toa READ signal comprises: the

5 propr'nte time. The ADDRESS shift register and gate 29 provide anoutput only when the incoming interrogation signal contain the addresscode ofthe particular SRU being interlogated. An output fran thiscircuit is required in order for any data to be sent back to the mesagecenter. The READ READ signal given, the ADDRESS ofthc' SRU.and thelocally gate (8 bone cfthrce function gates in the SRU. The READ storedinformation. This seemingly roundabout readout serves several importantfunctions. For example. it acknowledges D the message center that therequested function is to be performed. Also. by having a read out ofinformation n this manner, the source of the information isautomatically identified since the ADDRESS signal precedes theinformation.

Any data in the data storage shift register 36 is the result of an entryfrom keyboard 39. As any one of the lteys is pressed,

the character is first converted to a binary coded output in keyboardmatrix 40. This output is then transferred to the intermediate shiftregister 38 and stored. Depression of any of the keys also re ults in aKEY output from the keyboard matrix. This KEY pulse persists long enoughto gate the next RESET pulse through gate 41 and thus turn on 8" clockconverter 37.

The "8 clock converter then produces clock pulses which transfer thekeyboard data out of the intermediate registercounter and into the datastorage shift register. Note that since the RESET pulse is required, thekeyboard data is not transferred into the storage shifi register untilthe beginning of the message following the reset pyalse. The clockpulses then being produced by converter 37 ocur simultaneously with theclock pulses produced by converter 31. The first bit of the incomingdata stream. which is a logic l," is shifted through the AD- DRESS shiftregister 29 and when this bit reaches intermediate tap 42 it results inan output which turns off 3'' clock converter 37 through the read-insection. Thus only a sufficient number of clock pulses are produced byclock converter 37 to fully read out intermediate register 38 during akeyboard entry and the clock pulses shift the data out of temporarystorage in the intermediate register-counter into the data storage shiftregister 36.

The contents of the data storage register are displayed on characterdisplay 43 after the data storage register outputs have been translatedinto a suitable format by display matrix 44. Data entered into the datastorage register 36 will remain there until the SRU is cleared,accomplished either by locally entering a CLEAR signal into the SRU orby an incoming CLEAR signal from the message center. While the localentry of information requires a local clock signal. it should be notedthat the clock is always available from the message center. whether ornot the particular SRU is addressed.

For purposes of describing the operation of the SRU, the circuitry hasbeen subdivided into a number of separate functions. The resultingfunctional block diagrams are shown in F lGS. 36. Each figure does notshow all the actual interconnections between the functional units butmerely enough interconnectionsto indicate the signal flow through thesystem. A composite of these four figures would. however, indicate theinterconnections of the functional units.

The elements of FIGS. 3-6 are set forth below and briefly function Iused when the message center interrogates the SRU tosee whetheranyinformation is ready to be transmitted back to the mesage center. TheREAD gate 48 responds each time the proper READ code appears in theincoming signal.

However, response of the SRU to the READ signal also depends on whetherthe ADDRESS gate 29 has also responded. These conditions are sat'mfiedwhen a flip-flop, called the mmge flip-flop {Ml-T) is switched to thelogic "lstate. This flip-flop, in turn. controls a number of othercircuits in the SRU.

Following the entry of keyboard data into the SRU data storage registers36'. the information will normally be sent to the message centeron thenext correctly addressed READ in- 2 terrogatim following local entry ofa TRANSMlT signal into the SRU, under the control of the transmit-clearcontrol circuit 4. There is one other input to the transmit section ofthis control and that is the TRANSMlT HOLD operation. The TRANSMIT HOLDsignal comes from the keyboard or other input device. This assures thatthe SRU stays in the transmit mode when the keyboard is sending outinformation. When the keyboard or input device is in the receive orstandby mode, no signal is applied to this input and there is not effecton the operation of the transmit circuit.

The COMMAND order is used to direct the SRU to take information comingin from the message center and store this information in the datastorage shift registers 36'. This information may then be used to drivea display in the SRU. as. for example. a teletypewriter. or to controlsome remote function.

REcognition of the COMMAND signal is performed by the command gate andflip-flop 50.

Tile COMMAND gate 50 is a combination NOR-AND gate with its inputs takenfrom the F UNCT lON shift register. if the outputs of the FUNCHON shiftregister are correct at the 45 time the ADDRESS gate pulse is receivedthen the COM- MAIN'D gate output will set the command flip-flop to thelogic I state. As with he other functions. this assures that the SRUwill respond only to a COMMAND signal intended for it 5 and only at theproper time in the received signal period.

Thel-ocal data section clock converter 51 provides the local clocksignals for reading keyboard data into the data storage shift register36'. for entering data during a COMMAND order, and for moving the dataout of the data storage shift register when the SRU is being read.Provision is also made for clearing the display shift registers to zero.The data storage shift registers 36 represents a combination of elements36 and 38 ashown in FIG. 2.

Tl-le rcad-in control circuit 52 produces one input to the clockcontrolofthe local data section clock converter 5! during entry of information.The readout control circuit 53 prorida the second input to the localdata section clock conrates-5!. Theoutput oftha circuit is from areadout flip-flop, contained therein, and it controls the generation ofthe local described. Then the mode of operation illustrated by each of55 clock pulses for transferring the digital data stored in the dataFlGS. 3-6 will be described in detail. in FIGS. 3-6 the interrogationclock converter 45 receives the input CLOCK signal and converts it intoa local clock signal suitable for clocking the ADDRESS and FUNCTIONshift registers 29 and 30 and the return signal output shift register46. A RESET pulse serves to clear all shift registers driven by thisclock converter. There are two principal data messages handled withinthe SRU. One of these is contained in the incoming forward transmissionsignal and the second data message is that entered lostorage shiftregisters outof the registers for transmission back Iothe messagecenter. A second use of the readout flip-flop '5 Iocontro' the clockwhen data are read into the SRU through theCOMMAND function.

The character d'splay 43 may comprise any suitable display pliated callyinto the SRU via a keyboard or other input device. The playfl's led by adisplay matrix 44 which serves as an inter- 7eeberweenthe'mtermeriaterefirerlandthecharncter air u a Consderingthevariousmodesofopentionofthe SRUinmmlillrnratesthebaldaaentrymodeinwhichinformatimatthemhscriher'slocationisitsertedintotheSRU fra'transfertothemesagecentenbthismodeofoperation.mn'ngakey'boordinpugch'actersignalsfrom keyboard JDaretransformedintobinarycode bylteyboard matrix 40 ndappliedtodatastorageregisterMfiThe keyboard matrix OdsoaendsaKEYsignaltoread-incontrolcircuit 52 lherebyndvat'mgkTheread-inctmtrolcircuitSZ activatesthebcaldatasectionclockconvertersl whichthen providesdockpulscsenablingthekeyboarddatatoreadintodata storage register 36'.The KEY s'gnal also prevents further reset signals from interrupting theentering of information. The display matrix 44 further includes meansfor adjusting the read-in of information to ensure proper entry. Thisoutput of the display matrix is coupled through data delay circuit 47 toADDRESS register 29. This reg'ster then serves to terminate the localclock. signals by the read-in control circuir upon completion of dataentry.

The READ function is illustrated 'm FIG. 4 and is performed as follows-The incoming sigrul from the message center puses through delay 47 andenters registers 29 and 30. The simultaneous outputs representing theproper ADDRESS from 29 and the READ function from 30 activate the readgate and message flip-flop 48. The transmit-clear controlcircuit-l9iscoupledtotheftutctionregister30andenables the readout totake place; i.e.. a TRANSMIT signal must be locally entered in order forthe information within the SRU to be read out. otherwise the SRU willonly return the ADDRESS and FUNCTION signals. REturning these signals tothe message center serves to indicate properoperation ofthe SRU to themessage center.

As the data storage register 36' is read our. the information flows outas discussed in connection with FIG. 2. viz, the FUNCTION (READ).ADDRESS. and information signals follow one another seriatim through thereturn signal register 46 while the information is read back into thedata storage reg'eter 3" in the event it must be reread. The countercontained in 36'. as in FIG. 2. assures that the data storage registeris read out only once per READ signal. At the end of a readout, thecounter in 36 disables readout control circuit 53, thereby stopping thereadout.

The response ofthe SRu to a CLEAR signal '5 illustrated in FIG. 5. Inthis mode of operation, a properly addressed. CLEAR function signal isreceived via data delay circuit 47 and identified in registers 29 and3.. This signal generally follows the proper reception of information bythe message center and clears register 36' of the information cycledback into it during readout. Upon receipt of the proper outputs from theregisters 29 and 30. the message flip-flop is set. thereby enabling theclear control c'ncuit 49 to clear the infornation out of data storageregister 36' via clock converter which is also activated. The clearingof register 36' also clears display interface 44. This serves to erasecharacter display andindicatetothcsubscribertlnthismesage has beenreceived. Obviously, any suitable form of proper receipt indicator couldalso be activated.

The clearfunction may also heperforlned by the subscriber by locallyinserting a CLEAR signal directly into transmitclear control 49. Thiswould be done. for example. if an error were ntak entering informationlocally into data storage refiterllfl'flrisCLEARsignalrnaybemadetoerascall or ody part ofthe information stored in data storage register 36'.

no. 6 ilustrates the response of the Ski: to the COM- HAND functionsignal. In this mode of operation. information horn the mesage center isentered into the data storage register 36 ofthe SRU. It is in responseto this COMMAND function signal tint the SRU may Gsrlay the informationreceived and/or carry out particular taZ-s. determined by themcesnoryequipment controlled bytkSRU,

lntheCUMMANDmodeofoperatim-bd'oretheaddressregister29identifiesthesignaltherebysettingthemesage flip-flop in 48.11: function registeraardtheotnput ofthe setmeaage flip-flop activate the conrnadgate and flip-flop 50 which. aspreviously mentioned. emhla the readout control circuit 53. The readoutcontrd circuit controls local data section clock converter 51w'h'cllfllerata the clockrignalnecessarytotransfertheinformatinnfrunthemessage center into the data storage register I. 118 'mlormation isentered via the line connecting fumtimshift register 30 and data storageregister 36'. The tfisphy matrix 44 and character display 43 thenpresent the informtinn to II: subscriber.

While one embodiment of the present invention ha been described. it willbe apparent to those skills! the art that various changes may be made.For example. various error checking techniques have not been discussedsince there are several conventional techniques compatible with thepresent invention. urther. the present invention may be sufficientlyaccurate for many uses without the added apparatus and expense necessaryfor en'or checking. Also. error would depend upon the infonnationtransmission rate and the of the components used in making the presentinventirn.

While the present invention has been described as one terminal portionof a communication system, tlis is not to say that the functions of SRUand message center could not be combined to form an intermediate messagecenter. For example, several smaller subscriber service areas could becombined by coupling several intermediate message centers to a largercentral message center. This would he a horizontal or territorialcombination. The SRUs and mesag: centers could also be combined byfunction, i.e.. vertically, where several message centers serve the samearea but serve different functions. For exampie. one message centerwould serve commercial interests. department stores and the like. Sincethe SRU is designed to be used with television. to provide a completecommunication link. a store could have an advertisement on televisionand take orders from subscribers. Another message center would serveeducational interests. Books could be ordered from libraries or. wherespecific information is required from a large reference work. thenecessary ilentification of the work is sent to the library, themicrofilm card containing the information is selected. the appropriateportion is enlarged. and the picture is transmitted to the nabscribervia a vacant TV channel. Scientific and other interests could besimilarly served. This vertical combination is posible by virtue of thereturn signal register 46 which enable prefnting the message sent backto a message center. ie reorrn-addres coding.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A subscriber response unit comprising:

receiving means for receiving an incoming data signal.

wherein the first data bit is a logic 1"; address-recognition meanscoupled to said receiving means for decoding said data signal andproduc'mg m enabling output signal only if the address in said chtaignal corresponch to the predetermined address if nil addressrecognition means;

function recognition means. coupled m Sid receiving means. having aplurality of outputs corresprxtling one each to a plurality offunctions. for decoding aid incoming data signal and producing anenablingsignalonone of its outputs and depending upon the funct'nu b beperformed as encoded on said data signal.

local data entry means for enabling the sdncrmertoenter local datasignals into the subscriber respmne unit.

ta storage means for storing information portions d the received datasignal and information portion of locally entered data signals;

output means coupled to said data storage calm means for performing thefunction indicated by the received data signal in response tos'aidlogicl"anda denabl'm;

signals from said address and function recognition means and forperforming the functiors indicated by said local data signals. 2. Asubscriber response unit as set forth in claim I wherein said outputmeans comprises;

display matrix means for converting the output of said data storagemeans into a form suitable for display. and

character-display means coupled to said display-matrix means fordisplaying the output of said data storage means.

3. A subscriber response unit as set forth in claim I wherein saidoutput means comprises:

control means for carrying out operations automatically at the locationof the subscriber response unit under the control of the output of thedata storage means.

4. A subscriber response unit as set forth in claim 1 wherein said meansfor performing the function indicated by the received data signalcomprises:

read control means responsive to said enabling signals from said addressand function recognition means and said logic l in said functionrecognition means readout means responsive to said READ output signalfor reading out said data storage means.

5. A subscriber response unit as set forth in claim 6 wherein saidreadout means comprises:

flip-flop means going into a logic I state in response to said READoutput signal, ,gyitch means. responsive to said flip-flop means goinginto the logic I state. for connecting said address recognition means tosaid data storage means, and gating means coupled to said functionrecognition means and responsive to the logic I" state of said flip-flopfor allowing the function recognition means to be read out, whereby asignal will be sent out by the subscriberresponse unit identifyingitself. the function it is performing. and giving the desiredinformation from its data storage means. 6. A subscriber-response unitas set forth in claim wherein said readout means further comprises:

means for recycling the information read out of said data storage meansback into the data storage means to preserve said information in theevent it must be read out again. 7. A subscriber response unit as setforth in claim 6 wherein said readout means further comprises:

clearing means for clearing said data storage means of informationrecycled back into said data storage means uponproperreadrxitofsaidmbscriber-responseun'n.lAsubscriberreqaormtmitassetforthinclaim I furtherloezdclockoonvertingmeansforprodudnga localclock 5signalforthembscriber-responsemitinresponsetoa clock signal received bythe subscriber-response unit. andwhereinsaidlocaldmentry'scontrolledbysaid local clock signal. 9.Ambscnber-responsem'nassetforth in claim 8 wherein 10 said local dataentry means compr'aa a device utilizing a keyboard fiir use by a humanoperator.

1.. A subscriber-response unit as set forth in claim 8 wherein saidmeans comprises means for a COMMAND code in said incoming data signal l5and generating a command enabling signal at one of said funemeansoutputs. and said means for performing the function indicated by thereceived data signal comprsu:

means responsive to the enabling output signal of said addrm recognitionmeats and said command enabling signal for entering information fromsaid received incoming data signal into said data storage means underthe control of said local clock signal. 11. A subscriber-response unitas set forth in claim 10 wherein said output means comprises:

display matrix means for converting the output of said data storagemeans intoa form suitable for dis lay. and character display meanscoupled to display matrix means for d'splaying the output of said datastorage means.

12. A subcriber-nesponse unit as set forth in claim l0 wherein saidoutput meats comprises:

control means for carrying out operations automatically at the locationof the subscriber-response unit under the control of the output of thedata storage means. whereby said subscriber-response unit can act as aremote control unit in response tosaid received incoming data signal anda a local control unit in response to said local data signals.

IS. A subscribe tuponse unit as set forth i claim I wherein said meansfor performing the function indicated by the received data signalcomprises:

clear control means responsive to enabling signals from said addres andfunction-recognition means for producing a CLEAR output and meansresponsive to said CLEAR output signal for clearing dwa from said datastorage means i O O UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3. 2 03 Dated November 23, 1971 Inventor(s) TerryL Hewitt It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 9 line 21 after "means" insert to produce a READ output signal,

Colunm 9 line 24 cancel "6 and insert 4-- Column 10 ,line 40 cancel "i"and insert in Signed and sealed this 1st day of May 1973.

Attest:

LLUJARL ll. FLLTCHJW, J1 ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents uscoMM-oc 6O375-P59 U 5 GOVERNHENY PHINYINGOFFICE: 959 0-366-334

1. A subscriber response unit comprising: receiving means for receiving an incoming data signal, wherein the first data bit is a logic ''''1''''; address-recognition means coupled to said receiving means for decoding said data signal and producing an enabling output signal only if the address in said data signal corresponds to the predetermined address of said address-recognition means; function recognition means, coupled to said receiving means, having a plurality of outputs corresponding one each to a plurality of functions, for decoding said incoming data signal and producing an enabling signal on one of its outputs and depending upon the function to be performed as encoded on said data signal, local data entry means for enabling the subscriber to enter local data signals into the subscriber response unit, data storage means for storing information portions of the received data signal and information portions of locally entered data signals; output means coupled to said data storage means; means for performing the function indicated by the received data signal in response to said logic ''''1'''' and said enabling signals from said address and function recognition means and for performing the functions indicated by said local data signals.
 2. A subscriber response unit as set forth in claim 1 wherein said output means comprises; display matrix means for converting the output of said data storage means into a form suitable for display, and character-display means coupled to said display-matrix means for displaying the output of said data storage means.
 3. A subscriber response unit as set forth in claim 1 wherein said output means comprises: control means for carrying out operations automatically at the location of the subscriber response unit under the control of the output of the data storage means.
 4. A subscriber response unit as set forth in claim 1 wherein said means for performing the function indicated by the received data signal comprises: read control means responsive to said enabling signals from said address and function recognition means and said logic ''''1'''' in said function recognition means readout means responsive to said READ output signal for reading out said data storage means.
 5. A subscriber response unit as set forth in claim 6 wherein said readout means comprises: flip-flop means going into a logic ''''1'''' state in response to said READ output signal, switch means, responsive to said flip-flop means going into the logic ''''1'''' state, for connecting said address recognition means to said data storage means, and gating means coupled to said function recognition means and responsive to the logic ''''1'''' state of said flip-flop for allowing the function recognition means to be read out, whereby a signal will be sent out by the subscriber-response unit identifying itself, the function it is performing, and giving the desired information from its data storage means.
 6. A subscriber-response unit as set forth in claim 5 wherein said readout means further comprises: means for recycling the information read out of said data storage means back into the data storage means to preserve said information in the event it must be read out again.
 7. A subscriber response unit as set forth in claim 6 wherein said readout means further comprises: clearing means for clearing said data storage means of information recycled back into said data storage means upon proper readout of said subscriber-response unit.
 8. A subscriber response unit as set forth in claim 1 further comprising: local clock converting means for producing a local clock signal for the subscriber-response unit in response to a clock signal received by the subscriber-response unit, and wherein said local data entry is controlled by said local clock signal.
 9. A subscriber-response unit as set forth in claim 8 wherein said local data entry means comprises a device utilizing a keyboard for use by a human operator.
 10. A subscriber-response unit as set forth in claim 8 wherein said function-recognition means comprises means for recognizing a COMMAND code in said incoming data signal and generating a command enabling signal at one of said function-recognition means outputs, and said means for performing the function indicated by the received data signal comprises: means responsive to the enabling output signal of said address-recognition means and said command enabling signal for entering information from said received incoming data signal into said data storage means under the control of said local clock signal.
 11. A subscriber-response unit as set forth in claim 10 wherein said output means comprises: display matrix means for converting the output of said data storage means into a form suitable for display, and character display means coupled to said display matrix means for displaying the output of said data storage means.
 12. A subcriber-response unit as set forth in claim 10 wherein said output means comprises: control means for carrying out operations automatically at the location of the subscriber-response unit under the control of the output of the data storage means, whereby said subscriber-response unit can act as a remote control unit in response to said received incoming data signal and as a local control unit in response to said local data signals.
 13. A subscriber-response unit as set forth in claim 1 wherein said means for performing the function indicated by the received data signal comprises: clEar control means responsive to enabling signals from said address and function-recognition means for producing a CLEAR output signal, and means responsive to said CLEAR output signal for clearing data from said data storage means. 